The chemical conjugation of specific benzo(a)pyrene oxides and other epoxides to glutathione, enzymatically and non-enzymatically, is being investigated using nuclear magnetic resonance (NMR) spectroscopy, chemical synthesis, and high pressure liquid chromatography (HPLC). The regiospecificity and stereospecificity of the conjugation reaction is being determined. A HPLC assay has been developed for the glutathione conjugates of benzo(a)pyrene 4,5-oxide and the conjugation with various purified glutathione S-transferases examined for stereochemical detail. The stereochemistry of the isomers of the glutathione and mercapturic acid conjugates of styrene oxide has been established.